Formable composites are known for use in electrical applications. These composites are generally utilized as supporting substrates, insulating layers, and/or casements for electrical devices. Ideally, the composite materials provide excellent electrical and mechanical properties, e.g., high circuit density, low transmission energy loss, high strength, low weight, etc., and provide all desired characteristics at low cost. Problems still exist with attaining this ideal, however.
Formable composite materials generally include reinforcement fibers held in a polymer matrix, often with additional components as well to improve characteristics such as thermal conductivity, adhesion, color, etc. Unfortunately, the components that make up the composite, while supporting one or more desired properties, often detract from others. For instance, glass fibers can offer excellent tensile strength characteristics, but have a dielectric constant of about 6, and thus are often unsuitable for low transmission energy loss applications, particularly if used in abundance. Accordingly, glass fibers have been combined with resins that exhibit desirable electrical characteristics to form composites having acceptable electrical as well as physical properties, though at the cost of compromising somewhat on overall performance.
Polymeric materials have been utilized to provide fibrous reinforcement in composites. For instance, fibers formed of engineering polymers such as ultra-high molecular weight polyethylene (UHMWPE) have been examined as have a variety of polyaramid fibers. Problems still exist with these materials as well. For instance, UHMWPE fibers can have good electrical characteristics, but have a low temperature resistance, with a melt temperature around 135° C., and thus cannot be used in high temperature applications. Polyaramid fibers, while they can be quite strong, also have limited temperature resistance and often exhibit unacceptably high loss. In addition, these highly engineered polymers are often quite expensive to formulate and process.
While there have been improvements in materials and methods for forming composites for use in electrical applications, there remains room for further improvement and variation within the art.